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DRINKING WATER DISINFECTION BYPRODUCTS AND DURATION OF GESTATION
Citation:
HOFFMAN, C., P. MENDOLA, D. A. SAVITZ, A. H. HERRING, D. P. LOOMIS, AND A. OLSHAN. DRINKING WATER DISINFECTION BYPRODUCTS AND DURATION OF GESTATION. Presented at Society for Epidemiologic Research (SER), Boston, MA, June 20 - 23, 2007.
Impact/Purpose:
Presentation
Description:
Recent studies of drinking water disinfection by-products (DBPs) suggest high exposure decreases risk of preterm birth. We examined this association with total trihalomethane (TTHM) and five haloacetic acids (HAA5) among 2,041 women in a prospective pregnancy study conducted from 2000-2004. Study sites were chosen to provide a broad range of DBP exposure across sites, with minimal spatial variability in concentrations within sites. Participant data were collected through interviews, an early ultrasound and birth records. Weekly water samples were collected over the study period. The association between residential DBP levels and preterm birth (< 37 weeks' gestation) was assessed using multiple log-binomial regression. Discrete-time hazard analysis was used to model the conditional odds of delivery each week in relation to DBP exposure, allowing time-varying coefficients. Average second-trimester TTHM and HAA5 were inversely associated with preterm birth risk. Risk ratios (95% confidence interval) for TTHM levels of 30-59, 60-79, and ≥ 80 versus ≤ 5 µg/L were 0.9 (0.6,1.4), 0.7 (0.5,1.1) and 0.5 (0.2, 1.0) (p-value for trend: 0.04). Risk ratios for HAA5 levels of 18-29 and ≥ 30 versus ≤ 1 µg/L were 1.0 (0.7,1.4) and 0.6 (0.4,0.9) (p-value for trend: 0.01). The conditional odds of delivery each week were decreased for high TTHM and HAA5 exposure compared to the low exposure group for gestational weeks' 36-40 (odds ratios ranged from 0.6-0.9 for TTHM and 0.4 to 0.9 for HAA5), but then increased after 40 weeks' (odds ratios ranged from 2.2-7.2). Results corroborate the findings of other recent studies and suggest that high DBP exposure may be associated with delayed birth throughout gestation.